Benchmark: Spread vs object assign array of objects

Tests:

Assign
const a = { Color: 'red', Font: 'big' }; const colA = [ { Name: 'cola' }, { Name: 'colb' } ]; colA.forEach(item => { Object.assign(item, a); });
Spread
const a = { Color: 'red', Font: 'big' }; const colA = [ { Name: 'cola', ...a }, { Name: 'colb', ...a } ];
For for
const a = { Color: 'red', Font: 'big' }; const colA = [ { Name: 'cola' }, { Name: 'colb' } ]; for (let i = 0; i < colA.length; i++) { const item = colA[i]; for (const key in a) { item[key] = a[key]; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Assign
Spread
For for

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

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Let's break down the provided benchmark and explain what's being tested, compared, and their pros and cons.

**Benchmark Overview**

The benchmark tests three different ways to assign values to an array of objects in JavaScript: `Object.assign()`, spread operator (`...`), and a traditional `for` loop. The test cases are designed to measure the performance difference between these approaches.

**Individual Test Cases**

1. **Assign**
	* Benchmark Definition:
```javascript
const a = {
  Color: 'red',
  Font: 'big'
};

const colA = [
  {
    Name: 'cola'
  },
  {
    Name: 'colb'
  }
];

colA.forEach(item => {
  Object.assign(item, a);
});
```
	* This test case uses `Object.assign()` to assign the values of object `a` to each item in the array `colA`.
	* The pros of this approach are:
		+ Easy to read and write.
		+ Works with any type of object (arrays, objects, etc.).
	* The cons are:
		+ Can be slower than other methods for large arrays.
2. **Spread**
	* Benchmark Definition:
```javascript
const a = {
  Color: 'red',
  Font: 'big'
};

const colA = [
  {
    Name: 'cola', 
    ...a
  },
  {
    Name: 'colb', 
    ...a
  }
];
```
	* This test case uses the spread operator (`...`) to assign the values of object `a` to each item in the array `colA`.
	* The pros of this approach are:
		+ Can be faster than `Object.assign()` for large arrays.
		+ More concise and readable.
3. **For Loop**
	* Benchmark Definition:
```javascript
const a = {
  Color: 'red',
  Font: 'big'
};

const colA = [
  {
    Name: 'cola'
  },
  {
    Name: 'colb'
  }
];

for (let i = 0; i < colA.length; i++) {
  const item = colA[i];
  for (const key in a) {
    item[key] = a[key];
  }
}
```
	* This test case uses a traditional `for` loop to assign the values of object `a` to each item in the array `colA`.
	* The pros of this approach are:
		+ Can be more control over the assignment process.
	* The cons are:
		+ More verbose and harder to read.

**Library**

There is no specific library used in this benchmark. The `Object.assign()` method is a built-in JavaScript function, while the spread operator (`...`) is also a built-in feature of the language.

**Special JS Feature**

The spread operator (`...`) is a relatively recent addition to JavaScript (introduced in ECMAScript 2018). It allows objects or arrays to be expanded into new properties or elements.

**Benchmark Results**

The latest benchmark results show that:

1. **For Loop**: The fastest execution per second, with an average of 2678577.25.
2. **Spread**: Faster than the `Object.assign()` method, with an average of 7350182.5 executions per second.
3. **Assign**: The slowest approach, with an average of 19460540.0 executions per second.

**Other Alternatives**

If you're looking for alternative ways to assign values to arrays of objects in JavaScript, some other options include:

1. `Array.prototype.map()`: This method returns a new array with the results of applying the provided function to each element.
2. `Array.prototype.forEach()` followed by a loop: Similar to the traditional `for` loop approach, but using an arrow function or a callback function.

These alternatives may offer different trade-offs in terms of performance, readability, and conciseness.

Related benchmarks:

Spread vs object assign array of objects (version: 0)

Comparing performance of: Assign vs Spread vs For for

Created: 2 years ago by: Guest

Jump to the latest result

Assign

Spread

For for

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):